1. Field
Embodiments relate to rebalancing of the first extents of logical volumes among a plurality of ranks.
2. Background
In certain storage system environments, a storage controller (or a storage controller complex) may comprise a plurality of storage servers that are coupled to each other. The storage controller allows host computing systems to perform input/output (I/O) operations with storage devices controlled by the storage controller, where the host computing systems may be referred to as hosts.
The physical storage space in the storage devices controlled by the storage controller may be present in a plurality of physical storage volumes. For example, a physical storage disk may be divided into a plurality of physical storage volumes. The hosts send requests for I/O operations with respect to logical storage volumes (also referred to as logical volumes) to the storage controller, and the storage controller may perform the mapping of the logical storage volumes to the physical storage volumes and execute the I/O operations. A logical storage volume may be comprised of a plurality of extents, where an extent is a unit of storage, such as a set of data blocks.
Redundant array of independent disks (RAID) is a data storage virtualization technology that combines a plurality of physical disk drive components into a single logical unit for the purposes of data redundancy, performance improvement, or both. A rank is a logically contiguous storage space, and ranks used in a RAID configuration are referred to as RAID ranks. The extents of a plurality of logical storage volumes are distributed in a plurality of RAID ranks and may be managed by a storage controller.
Further details of a storage controller may be found in the publication entitled “IBM DS8880 Architecture and Implementation (Release 8.2.1)”, published January 2017 by the International Technical Support Organization of International Business Machines (IBM*) Corporation.